This invention relates to an apparatus for grinding an edge shape and peripheral surface configuration upon ophthalmic lenses.
The art of preparing ophthalmic lenses from glass blanks entails two major processes. First, the circular lens blanks are surface ground with a prescriptive front and back curvature to provide a desired optic quality or characteristic and thus enhance the vision of an ultimate wearer. Secondly, the lenses are ground to a desired edge shape to fit a preselected frame. Additionally, the peripheral edge surface of lenses are typically beveled or finished to cooperate with a reciprocal bevel on an interior peripheral surface of a frame in order to hold the lenses within the frame.
In the past at least one process of lens edging has been achieved by mounting a single lens upon a laterally fixed spindle or chucking mechanism and advancing an abrading wheel into lateral contact with the lens. The process is then repeated on an additional blank to produce a matching set or pair of lenses.
In another previously known process a lens to be edge ground is horizontally mounted about a vertical axis. A pair of grinding wheels are vertically mounted for rotation on either side of the lens for selective advancement into grinding engagement with the central lens. Each of the grinding wheels is fashioned with an oppositely sloping peripheral surface. Accordingly, one wheel contacts a front peripheral portion of the lens and the other wheel contacts a back peripheral portion of the lens. In combination the two grinding wheels form a beveled peripheral edge on the lens. Lateral control of the abrading wheels is achieved by a pair of conical cam followers which ride against a generally disc shaped cam. Once completed the lens is removed and the process is repeated on a second lens blank to produce a pair.
Although lens edging equipment of the foregoing and similar designs have received at least a degree of attention and acceptance in the art, room for improvement remains.
In this connection, edge grinding a pair of lenses on presently known machines is somewhat time consuming and requires a degree of operator attention and control.
Additionally, previously known edging devices are limited to grinding a single lens at one time and thus lack a certain degree of uniformity and symmetry desired of a pair of lenses.
Further, presently known machines do not provide a capability for edging a pair of lenses in a manner to sequentially remove excess glass and then fine grind a desired edge configuration.
Still further, the known prior art devices do not exhibit a capability for simultaneously grinding a pair of lenses or facilely varying the size for a given lens shape.
The difficulties suggested in the preceeding are not intended to be exhaustive, but rather are among many which may tend to reduce the effectiveness and user satisfaction of prior lens edging methods and apparatus. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that ophthalmic lens edging machines and techniques appearing in the past will admit to worthwhile improvement.